US2395911A

US2395911A - Piston and guide structure for engines of the reciprocating piston type

Info

Publication number: US2395911A
Application number: US467079A
Authority: US
Inventors: Schoenfeld Joseph
Original assignee: Individual
Current assignee: Individual
Priority date: 1942-11-27
Filing date: 1942-11-27
Publication date: 1946-03-05
Anticipated expiration: 1963-03-05

Description

March 5, 1946. J SCHOENFELD 2,395,911 PISTON AND GUIDE STRUCTURE FOR ENGINES OF.THE RECIPROCATING PISTON TYPE Filed NOV-27, 1942 2 Sheets-Sheet 1 VEN TOR. I Jszmfiz /amm March 5 1946. sc o 2,395,911 PISTON AND GUIDE STRUCTURE FOR ENGINES OF THE RECIPROGATING PISTON TYPE Filed Nov. 2'7, 1942 2 Sheets-Sheet 2 @atented Mar.

UNITE PISTON AND GUIDE STRUCTURE FOR: ENGINES OF THE RECIPROCATING PIS- TON TYPE Joseph Schoenfeld, Fairfax, can. Application November 27, 1942, Serial No. 467,079.

Claims. (01. 74-44) 'I'his'invention relates to a piston and guide structure for engines of the reciprocating piston type, this application being a continuation in part of my application entitled "Piston and guide for internal combustion engines," filed June 14, 1941,

Serial Number 398,018.

The object of the present inveiitionis generally to improve and simplify the construction and operation of pistons of engines of the reciprocating piston type; to reduce the length and weight of the piston and especially to provide a short piston and an auxiliary guide therefor, whereby any tendency of the piston to cook, tilt, or bind with relation to the cylinder wall is entirely eliminated.

cylinder engine, said section showing the piston and guide structure;

Fig. 2-is a vertical central sectiontaken on line II1I of Fig. 1;

Fig. 3 shows a modification of the piston structure of Figs. 1 and 2;

Fig. 4 is a section similar to Fig. 1, but showing a modification ofthe piston guiding structure; and

Fig. 5 is a cross-section taken on line V-V of Fig. 4.

Inregard to the foregoing application, in an internal combustion engine particularly of the high speed type, piston friction constitutes by far the largest item in the list of mechanical losses. The most immediate and greatest cause of piston friction is the shearing of the oil film formed between the cylinder and piston and the power absorbed is dependentupon the thickness of the film, the viscosity of the oil, the area presented to the piston, and the speed.

The co-eflicient of friction between the piston and cylinder is very much higher than that of the bearings and is in great part due to thickening of the lubricant by partial carbonization, as the lubricating film, or oil is directly exposed to the flame of combustion and as such decidedly increases the resistance to shear. Another factor producing friction is the pressure exerted by the piston against the cylinder wall due to the mertia of the reciprocating parts, and the area of contact between piston and cylinder. The length of nalcombustion engine requirements: I

1. Shouldreduce friction to the lowest possible limit. 1

2. Must rapidly dissipate heat to the walls of the cylinder.

should fulfill the following 3.'Must prevent passage oflubricating oil tothe combustion chamber.

4. Should have a minimum of weight.

5. Must provide an adequate support for the wrist pin.

6. Must be adequatelygulded to prevent tilting or binding with relation to the cylinder walls.

Requirements 1 and 4 are largely interdependent as the major portion of the average pressure exerted by the piston against the cylinder wall is in any high speed engine, due to the resolved component of the inertia forces, hence if the weight is reduced, inertia forces are reduced, and thecontact surface between the piston cylinder may be reduced in proportion to weight reduction. I A piston structure fulfilling the requirements enumerated, forms the subject matter of the presentapplicatlon, and will now be described in detail:

Referring to Fig. 1, A indicates the cylinder of an engine, B, the piston, C the connecting rod,

and D the crank shaft to which the piston and rod are connected. The piston proper comprises a head or crown portion 1. a ring portion 8 carrying a suitable number of rings 8, and bosses or bearing lugs In to receive and secure a wrist pin ii. The bearing lugs are cast integral with the ring portion 8 and are connected with the crown i by one or more ribs 82 so as to provide an adequate support for the wrist pin.

The piston, as will be noted, is exceptionally short in proportion to its diameter and as such would have a tendency to cook or tilt about the wrist pin with a resultant tendency to bind or seize with relation to the cylinder wall. To prevent such seizure, a guide is provided consisting of a rod or tube I4 which is secured at its upper end by threads l5 or other means to a central bearinglug', Illa. The lower end of the rod extends through a'gulde bearing 16 which in turn is supported in a cross-bracket l1 secured to the 2 asoaou this being probably the preferred type of structure. Whether one or two guide rods are employed, they are rigidly secured to the piston at their upper ends and must either have ample clearance where they pass through the guide hearings or the guide bearings must have a slight lateral movement as there would otherwise be a tendency to bind, particularly after the clearance between the piston and the cylinder wall has increased by wear. That is, nomatter how well a piston is fitted with relation to the .cylinder, a certain amountpf clearance must be provided; first to permit an oil film to be formed between the piston and cylinder wall, and secondly to allow for expansion of the-piston as it becomes heated during operation of the engine. This clearance maybeonivtim oi aninchwhen' an engine is new, butit becomes greater as wear the same clearance or it must be able to move laterally as the rod would otherwme tend to bend or bind. Such a bearing is shown in Fig. 2. .It is made in two halves, lid, which are supported in the bracket II and eachhalf is engaged by a compression spring i'la. Thus the guide bearing is yieldingly supported in the bracket and the guide rod may move laterally a limited distance,

larger ring section and more rings to rapidly dissi-.

pate heat to the cylinder wall and to prevent passage of oil into the combustion chamber.

with regard to area of surface between piston. and cylinder wall, it should be clear that only the surface at right angles to the line of the crank shaft is operative, the surface at the sides of the piston receive no thrust at all. .It is therefore clearly desirable to remove all inoperative surfaces in order to reduce, as far as pomble, the area of the oil film in shear. In view of the very light loading to which the piston is subjected, a relatively small area. of bearing surface suflices,

- and for a light weight piston such as here shown,

an actual bearing surface on either side equal to fifty percent of the area of the crown is more than ample, such surfaces in the form of shoes or slips as indicated at 25 in Fig. 3 will accordingly be provided if the ring portion area is not sumcient.

Whether one or more guide rods are employed, it is desirable that they be placed on a line which will intersect the longitudinal axis of the wrist pin and that they are disposed at right angles thereto so as to align with the longitude a ds of the cylinder. In Fig. 4 the guide rods are disposed one on each side of the connecting rod, however,

one guide rod can be employed and placed at one side of a conventional connecting rod but in that case a counterweight shouldbe pieced on-tbe opposite side of the piston to insure balance. The actual thrust or load to which the guide rod or rods are subjected is comparatively small; hence a thin walled tube of small diameter, or a channel shaped section as shown in Figs. 4 and 5, will more than sufilce and as this is the case, it will be obvious that whether one or two guide rods are used the weight added to the pistonis negligible. The advantages gained besidesthat of reducing the weight of the piston, the inertia forces, the

material reduction in friction due to the smaller friction and shear area presented, better heat transmission or dissipation to the cylinder. wall, etc., are a material reduction in the length of the cylinders as a shorter piston can operate in a shorter cylinder, the couple between the piston and crank shaft or in other words the length of the connecting rods may be also reduced, hence the overall height and weight of the engineas a whole is materially reduced.

While the piston and guide structure has been described for particular use in high speed internal combustion engines, itshould be understood that they are .equally adaptable .to other types of engines known as compressors, etc., employing a reciprocating piston, and while these and other features have been more or less specifically described, I wish it understood that changes may be resorted to within the scope of the appended claims, and that the materials and finish of the various parts employed may be varied as the experience of the manufacturer orvarying conditions or use may demand.

Having thus described my invention, what I claim and desire to secure by letters Patent is:

1. The combination with an engine having a cylinder, a piston, a crank shaft, a wrist pin in the piston and a connecting rod connecting the wrist pin and crank shaft to impart reciprocal movement to the piston, of an auxiliary guide rod rigidly secured to the piston at one endat one side of the connecting rodand at right angles to .the wrist pin, and a guide bearing adjacent an end of the cylinder through-which the other end of the guide rod extends, said guide rod and bearing securing the piston against tilting movement about the wrist Din.

2. The combination with an engine having a cylinder open at one end, a piston, in the cylinder a crank shaft and a connecting rod connecting the piston and crank shaft to impart reciprocal movement to the piston, of an auxiliary guide rod rigidly secured to the piston at one end, a guide bearing adjacent the open end of the cylinder through which the other end of the guide rod extends, said guide rod and bearing securing the piston against tilting movement with relation to the interior wall of the cylinder, and resilient means permitting lateral movement of the guide rod in the guide bearing to substantially conform with the lateral movement of the piston in the cylinder to permit the wall of the cylinder to support and guide the piston during reciprocal movement of the piston in the cylinder.

'3. The combination with an engine having a cylinder open at one end, av piston, in the cylinder a crank shaft, a wrist pin in the piston and a connecting rod connecting'the wrist pin and crank shaft to impart reciprocal movement to the piston, of an auxiliary guide rod rigidly secured to the piston at one endand at right angles to the wrist pin, a guide bearing adjacent the open end of the cylinder through which the other end of the guide rod extends, said guide rod and bear.

lateral movement of the piston in the cylinder to permit the wall of the cylinder to support and guide the piston during reciprocal movement of the piston in the cylinder.

4. The combination with an; engine having a cylinder, a piston, a crank shaft, a; wrist pin in the piston and a connecting rod connecting the wrist pin and crank shaft to impart reciprocal movement to the piston, of an auxiliary guide rod rigidly secured to the piston at ,one end and at right angles to the wrist pin, a guide bearing adjacent an end of the cylinder through which the other end of the guide rod extends, said guide rod and bearing securing the piston against tilting movement about the wrist pin, and resilient means permitting lateral movement of the guide bearing.

5. The combination with an engine having a cylinder, a piston, a crankshaft and a connecting rod connecting the piston and crank shaft to impart-reciprocal movement to the piston, of an auxiliary guide rod rigidly secured to the piston at one end, a guide bearing adjacent one end of the cylinder through which the other end of the guide rod extends, said guide rod and bearing securing the piston against tilting movement with relation to the interior wall of the cylinder, and resilient means permitting lateral movement of the guide bearing.

6. The combination with an engine having a cylinder, a piston, a crank shaft, a wrist pin in the piston and a connecting rod connecting the wrist pin and crank shaft to impart reciprocal movement to the piston, of an auxiliary guide rod rigidly secured to the piston at one end on a line intersecting the longitudinal axis-of the wrist pin and at right angles thereto, a guide bearing adjacent an end of the cylinder through which the other end of the guide rod extends, said guide rod and bearing securing'the piston against tilting movement about the wrist pin, and yielding means supporting the guide bearing to permit a limited lateral movement thereof.

7, The combination with an engine having a cylinder open at one end and a piston reciprocally mounted within the cylinder of an auxilingv rod connecting the wrist pin with a crank shaft to transmit reciprocal movement of the piston to rotate the crank shaft, said guide rod and bearing. preventing tilting of the piston aboutthe wrist pin during reciprocal movement. of the piston,

8. The combination with an engine having a cylinder open at one end, a piston reciprocally mounted within the cylinder, a crank shaft and a connecting rod pivotally connected to the piston at one end adjacent the crown thereof and to the crank shaft at the opposite end, said connecting rod being disposed centrally of the piston and cylinder of an auxiliar guide rod rig idly secured at one end to the piston at one side of the connecting rod and disposed on a line parallel to the longitudinal axis of the cylinder and piston, and an auxiliary guide bearing adjacent the open end of the cylinder through which the nected to the piston at one end and to the crank shaft at the oppositeend, said connecting rod being disposed centrally of the piston and cylinder of means for preventing tilting of the piston about the pivotal connection with the connecting rod, said means comprising an auxiliary guide rod rigidly secured at one end to the piston at one side of the connecting rod and disposed on a v line parallel to the longitudinal axis-of the cyl-- inder and piston and an auxiliary guide bearing adjacent the open end of the cylinder through which the other end of the auxiliary guide rod extends.

10. The combination with a trunk type engine having a cylinder open at one end, a trunk pis-V ton reciprocally mounted within the cylinder; a crank shaft and a connecting rod pivotally connected to the piston at one end and to the crank shaft at the opposite end, of means for preventiary guide rod rigidly secured at one end to the piston and disposed on a line parallel to the longitudinal axis of the piston and at one side thereof, a guide bearing adjacent the open end of the cylinderthrough which the other end of the rod extends, a wrist pin in the piston, and a connecting tilting of the piston about the pivotal connection with the connecting rod, said means com-. prising a pair of guide rods rigidly secured at one end to the piston, one on each side of the connecting rod and parallel to the longitudinal axis of the cylinder, and a pair of guide bearings adjacent the open end of the cylinder through which the opposite ends of the guide rods extend.-

' JOSEPH scnomw'mn.